The invention relates to a sheet feeder, imaging system incorporating the sheet feeder and a method. More particularly, the invention relates to a sheet feeder with a link member that maintains a constant stroke distance between a paper-engaging roller and an inclined paper ramp. The sheet feeder is particularly advantageous when incorporated into an imaging system, such as a printer or photocopier.
A quality imaging system requires consistent and error-free feeding of paper from a paper tray. A sheet of paper can become jammed immediately upon exiting the paper tray or at some location downstream in the paper path. Other times two or more pieces of paper are fed simultaneously from the paper tray to cause a jam or other misfunction. A great deal of effort is directed to providing paper imaging system features to avoid jamming or misfunction to overcome these problems.
One approach to reducing paper-feed error involves mounting a sheet-separating roller in a freely movable manner in a plane parallel to the stack of paper sheets. The roller moves as a function of the stiffness of the sheets. For example if a top sheet has a high stiffness, then the roller will move rearward until the front edge of the sheet is bent and urged up a receiving ramp. One of the drawbacks of such an approach is the relatively large number of parts required to move a roller proportionally to the stiffness of the sheet.
In view of the foregoing, there is a need for a sheet feeder, imaging system and method to feed paper sheets in a consistent and substantially error-free manner.
The invention relates to a sheet feeder, imaging system and method that provide paper feed in a consistent and substantially error-free manner. In one embodiment, the invention is an imaging subsystem for forming an image on a sheet. The subsystem comprises a tray for holding a supply of sheets, a ramp for directing a sheet from the tray to the imaging subsystem and a drive assembly including a roller for moving a top sheet of the supply of sheets in the tray to the ramp with a reciprocating roller stroke. The drive assembly is configured to maintain a constant roller stroke distance between the roller and the ramp.
In another embodiment, the invention relates to a sheet feeder for an imaging system, the sheet feeder comprising a linkage and a roller disposed on the linkage for contacting and driving a sheet from a supply of sheet material by a reciprocal linear movement through a roller stroke distance. The linkage is configured to maintain a constant roller stroke distance between the roller and the ramp.
Finally in an embodiment, the invention is a method for feeding sheets in an imaging system. In the method, a roller is moved in a reciprocating stroke to drive a sheet from a supply of sheets to a ramp that directs the sheet to an imaging subsystem. A constant distance is maintain ed for each stroke as the supply of sheets diminishes.